Field of the Invention
The present invention relates to a process for producing a cyclic hydrogenated silane compound.
Description of the Related Art
Thin film silicon is used for applications such as solar cells and semiconductors, and this thin film silicon has been conventionally prepared by a chemical vapor deposition method (CVD method) using a monosilane as a raw material. In recent years, a new producing method using a hydrogenated polysilane has attracted attention instead of the CVD method. This producing method is a coating film-forming method (a liquid process) in which a hydrogenated polysilane solution is applied to a substrate and then is calcinated, and cyclopentasilane, which is a cyclic hydrogenated silane, is used as a raw material for the hydrogenated polysilane solution. It has been reported that the cyclopentasilane is converted to a hydrogenated polysilane by UV irradiation (T. Shimoda et al., “Solution-processed silicon films and transistors”, Nature, vol. 440, p. 783 (2006)).
There is a possibility that a hydrogenated polysilane is synthesized also by using a cyclic hydrogenated silane compound other than cyclopentasilane as a raw material. As a cyclic hydrogenated silane compound, cyclohexasilane is known, other than cyclopentasilane. As a process for producing cyclohexasilane, for example, Japanese Patent No. 4519955 and WO 2011/094191 disclose a process for producing cyclohexasilane comprising the steps of preparing a salt of a halogenated cyclohexasilane dianion by contacting trichlorosilane with a tertiary polyamine such as N, N, N′, N″, N″-pentaethyl diethylenetriamine (pedeta) or N, N, N′, N′-tetraethyl ethylenediamine (teeda) to conduct cyclization coupling, and reducing it with a metal hydride. Japanese Unexamined Patent Publications No. 2014-12647 and No. 2014-12648 disclose a process for producing cyclohexasilane comprising the steps of preparing a salt of a halogenated cyclohexasilane dianion by contacting trichlorosilane with a phosphonium salt or an ammonium salt to conduct cyclization coupling, and reducing it with a metal hydride. E. Hengge et al. (“Preparation of cyclohexasilane, Si6H12”, Angew. Chem. Int. Ed. Engl., 16, p. 403 (1977)) discloses a process for producing cyclohexasilane comprising the steps of preparing dodecaphenylcyclohexasilane by reacting Ph2SiCl2 with an alkali metal to conduct cyclization coupling, reacting it with aluminum chloride to give dodecachlorocyclohexasilane, and reducing it with a metal hydride. J. Tillmann et al. (“Lewis acidity of Si6Cl12 and its role as convenient SiCl2 source”, Inorganic Chemistry, vol. 54, p. 9611 (2015)) discloses a process for producing dodecachlorocyclohexasilane comprising the steps of preparing a salt of a halogenated cyclohexasilane dianion by contacting hexachlorodisilane with a tetra-n-butylammonium salt to conduct cyclization coupling, and reacting it with aluminum chloride which is a Lewis acid, though it is not a process for producing cyclohexasilane.
As described above, conventionally, various processes for producing cyclic hydrogenated silane compounds or cyclic halosilane compounds have been proposed, and there is a demand for a process for more easily and efficiently producing a cyclic hydrogenated silane compound. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a process for efficiently producing a cyclic hydrogenated silane compound.